Coronary Heart Disease Risk Higher With Unhealthy Plant Food Diet

Researchers created 3 plant-based diet indices based on the healthiness of specific foods.

Consuming a plant-based diet index (PDI) that is rich in healthier plant foods is associated with a lower risk for coronary heart disease (CHD), but consuming “less healthy plant foods” may actually increase the risk for CHD, according to a study published in the Journal of the American College of Cardiology.

Ambika Satija, ScD, from the Harvard TH Chan School of Public Health in Boston, Massachusetts, and colleagues conducted a study to determine the associations between 3 plant-based diet indices and CHD in male and female health professionals in the United States.1

The researchers created the 3 versions of PDI using different grading approaches. An overall PDI included consumption of all plant food while reducing animal-derived food intake. A healthful PDI (hPDI) focused on intake of healthy plant foods associated with improved health outcomes, including whole grains, nuts/legumes, oils, and fruits and vegetables. Lastly, an unhealthful PDI (uPDI) involved consumption of less healthy plant foods such as juices/sweetened drinks, refined grains, potatoes/fries, sweets, and animal-derived foods, known to be associated with a higher risk for certain diseases.

The study population consisted of participants from the following studies: the Nurses' Health Study (NHS) which started in 1975 with 121,701 female registered nurses aged 30 to 55 years; NHS2 which started in 1989 with 116,686 registered nurses aged 25 to 42 years; and the Health Professionals Follow-Up Study (HPFS) that started in 1986 with 51,529 male health professionals aged 40 to 75 years. The population sample for the current study included 73,710 participants from NHS, 92,329 participants from NHS2, and 43,259 participants from HPFS.

To categorize participants into one of the three indices, the researchers provided semi-quantitative food frequency questionnaires every 2 to 4 years. Participants were asked to average how often they consumed a defined portion of approximately 130 food items separated into 18 food groups over the previous year. There were 9 response categories ranging from “never or less than once/month” to “greater than or equal to 6 times/day.”1

For PDI ratings, plant groups were given positive scores, while animal-derived food groups were given reversed scores. For hPDI ratings, healthy plant food groups were given positive scores, less healthy plant food groups and animal-derived food groups were given reversed scores; for uPDI ratings, less healthy plant food groups were given positive scores while healthy plant food groups and animal food groups were given reversed scores.

The results demonstrated that participants with higher scores on PDI and hPDI were older, more active, leaner, and less likely to smoke than participants with lower scores. Participants with high uPDI scores were younger, less active, and more likely to smoke than participants with lower scores.

With more than 4,833,042 person-years of follow up, 8631 participants developed CHD. In the NHS group, 3233 participants developed CHD compared with 667 participants in NHS2 and 4731 participants in HPFS. “PDI was modestly inversely associated with CHD incidence,” the researchers wrote.

An editorial comment added that a predominantly plant-based diet is associated with improved cardiovascular risk factors.2 “Until recently, as a group, cardiologists have not delved deeply into nutrition, treating [cardiovascular disease's] downstream effects rather than obliterating its roots, leaving primary and secondary prevention opportunities on the table. It is time that we educate ourselves on dietary patterns, risk, and outcomes, and focus more on ‘turning off the faucet' instead of ‘mopping up the floor.'”

Disclosures: Dr Chiuve is an employee of AbbVie, Inc. Dr Rimm has received financial support from the US Department of Agriculture/Blueberry Highbush Council and has served on the Scientific Advisory Committees of IKEA, Take C/O, and SPE. Dr Hu has received financial support from the California Walnut Commission and Metagenics.